<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let num = +prompt('请输入星期数')
        switch(num) {
            case 1 :
                alert('Monday')
            break
            case 2 :
                alert('Tuesday')
            break
            case 3 :
                alert('Wednesday')
            break
            case 4 :
                alert('Thursday')
            break
            case 5 :
                alert('Friday')
            break
            case 6 :
                alert('Saturday')
            break
            case 7 :
                alert('Sunday')
            break
            default:
                alert('请重新输入')
        }
    </script>
</body>
</html>